1. Field of the Invention
The present invention relates to a vehicle restraint system that limits lateral, longitudinal and yaw motions of a test vehicle on a simulated roadway, without substantially affecting handling properties of the vehicle.
2. Description of the Prior Art
In the prior art, simulated roadways and restraint systems for holding vehicles in position on such roadways have been advanced. A restraint system for use on conventional roller dynamometers is described in an article entitled "A Dynamometer On Which The Dynamic Behaviour Of A Passenger Car Can Be Simulated" by Jean Odier, published in Proc Instn Mech Engrs Vol 186, 1972, which describes a restraint for holding a vehicle in position on four independent, power driven roller dynamometers. The vehicle is restrained with a large cradle.
The linkage used required pivoting arms and actuators on both sides of the vehicle, with a single frame underneath the vehicle. In order to permit the necessary degrees of freedom, the linkages on opposite sides of the vehicle have to permit movement along and rotation about a vertical axis, they have to permit yaw motion, and also they have to permit lateral movement, which the restraint shown required system of horizontal slides for supporting the linkage. The linkage and frame takes substantial room, and because of the positioning of the main loading joints, called "spherical knee joints" in the article, and the fact that these joints provided all of the loading to the vehicle, there was a likelihood of "cross-talk" between loads in the various axes of interest.
Further, as pointed out in the article, there was a need for having sliding components, which are prone to high friction loads. Maintaining very low friction coefficients was essential to proper operation. The longitudinal restraint system in this prior art device was made so side loads and yaw could be simulated, but again it involved operating through a linkage that affected loading in other axes.
The same author, Jean Odier, has published additional papers in relation to the restraint device, including an analysis of braking system characteristics, in an article entitled "Road-Holding: Braking and Traction", Paper 700367, New York: Society of Automotive engineers, Inc., 1970, and an article entitled "Indoor Vehicle Braking Simulation: Correlation and Comparison with Road Testing", Paper 730,562, New York: Society of Automotive Enginners, Inc., 1973.
The vehicle restraint system shown in the first-mentioned article is also illustrated in a brochure from the French Farodo Group. It can be seen in the illustrations in such brochure that the prior restraint device requires a substantial amount of space, with space for access from both sides of the vehicle being required.